1 /* $NetBSD: kern_physio.c,v 1.42 2000/05/08 20:03:20 thorpej Exp $ */ 2 3 /*- 4 * Copyright (c) 1994 Christopher G. Demetriou 5 * Copyright (c) 1982, 1986, 1990, 1993 6 * The Regents of the University of California. All rights reserved. 7 * (c) UNIX System Laboratories, Inc. 8 * All or some portions of this file are derived from material licensed 9 * to the University of California by American Telephone and Telegraph 10 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 11 * the permission of UNIX System Laboratories, Inc. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * @(#)kern_physio.c 8.1 (Berkeley) 6/10/93 42 */ 43 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/buf.h> 47 #include <sys/malloc.h> 48 #include <sys/proc.h> 49 50 #include <vm/vm.h> 51 52 #include <uvm/uvm_extern.h> 53 54 /* 55 * The routines implemented in this file are described in: 56 * Leffler, et al.: The Design and Implementation of the 4.3BSD 57 * UNIX Operating System (Addison Welley, 1989) 58 * on pages 231-233. 59 * 60 * The routines "getphysbuf" and "putphysbuf" steal and return a swap 61 * buffer. Leffler, et al., says that swap buffers are used to do the 62 * I/O, so raw I/O requests don't have to be single-threaded. 63 */ 64 65 struct buf *getphysbuf __P((void)); 66 void putphysbuf __P((struct buf *bp)); 67 68 /* 69 * Do "physical I/O" on behalf of a user. "Physical I/O" is I/O directly 70 * from the raw device to user buffers, and bypasses the buffer cache. 71 * 72 * Comments in brackets are from Leffler, et al.'s pseudo-code implementation. 73 */ 74 int 75 physio(strategy, bp, dev, flags, minphys, uio) 76 void (*strategy) __P((struct buf *)); 77 struct buf *bp; 78 dev_t dev; 79 int flags; 80 void (*minphys) __P((struct buf *)); 81 struct uio *uio; 82 { 83 struct iovec *iovp; 84 struct proc *p = curproc; 85 int error, done, i, nobuf, s, todo; 86 87 error = 0; 88 flags &= B_READ | B_WRITE | B_ORDERED; 89 90 /* 91 * [check user read/write access to the data buffer] 92 * 93 * Check each iov one by one. Note that we know if we're reading or 94 * writing, so we ignore the uio's rw parameter. Also note that if 95 * we're doing a read, that's a *write* to user-space. 96 */ 97 if (uio->uio_segflg == UIO_USERSPACE) { 98 for (i = 0; i < uio->uio_iovcnt; i++) { 99 /* XXXCDC: map not locked, rethink */ 100 if (__predict_false(!uvm_useracc(uio->uio_iov[i].iov_base, 101 uio->uio_iov[i].iov_len, 102 (flags == B_READ) ? B_WRITE : B_READ))) 103 return (EFAULT); 104 } 105 } 106 107 /* Make sure we have a buffer, creating one if necessary. */ 108 if ((nobuf = (bp == NULL)) != 0) { 109 110 bp = getphysbuf(); 111 /* bp was just malloc'd so can't already be busy */ 112 bp->b_flags |= B_BUSY; 113 114 } else { 115 116 /* [raise the processor priority level to splbio;] */ 117 s = splbio(); 118 119 /* [while the buffer is marked busy] */ 120 while (bp->b_flags & B_BUSY) { 121 /* [mark the buffer wanted] */ 122 bp->b_flags |= B_WANTED; 123 /* [wait until the buffer is available] */ 124 tsleep((caddr_t)bp, PRIBIO+1, "physbuf", 0); 125 } 126 127 /* Mark it busy, so nobody else will use it. */ 128 bp->b_flags |= B_BUSY; 129 130 /* [lower the priority level] */ 131 splx(s); 132 133 } 134 135 /* [set up the fixed part of the buffer for a transfer] */ 136 bp->b_dev = dev; 137 bp->b_error = 0; 138 bp->b_proc = p; 139 LIST_INIT(&bp->b_dep); 140 141 /* 142 * [while there are data to transfer and no I/O error] 143 * Note that I/O errors are handled with a 'goto' at the bottom 144 * of the 'while' loop. 145 */ 146 for (i = 0; i < uio->uio_iovcnt; i++) { 147 iovp = &uio->uio_iov[i]; 148 while (iovp->iov_len > 0) { 149 /* 150 * [mark the buffer busy for physical I/O] 151 * (i.e. set B_PHYS (because it's an I/O to user 152 * memory, and B_RAW, because B_RAW is to be 153 * "Set by physio for raw transfers.", in addition 154 * to the "busy" and read/write flag.) 155 */ 156 bp->b_flags = B_BUSY | B_PHYS | B_RAW | flags; 157 158 /* [set up the buffer for a maximum-sized transfer] */ 159 bp->b_blkno = btodb(uio->uio_offset); 160 bp->b_bcount = iovp->iov_len; 161 bp->b_data = iovp->iov_base; 162 163 /* 164 * [call minphys to bound the tranfer size] 165 * and remember the amount of data to transfer, 166 * for later comparison. 167 */ 168 (*minphys)(bp); 169 todo = bp->b_bcount; 170 #ifdef DIAGNOSTIC 171 if (todo < 0) 172 panic("todo < 0; minphys broken"); 173 if (todo > MAXPHYS) 174 panic("todo > MAXPHYS; minphys broken"); 175 #endif 176 177 /* 178 * [lock the part of the user address space involved 179 * in the transfer] 180 * Beware vmapbuf(); it clobbers b_data and 181 * saves it in b_saveaddr. However, vunmapbuf() 182 * restores it. 183 */ 184 PHOLD(p); 185 if (__predict_false(uvm_vslock(p, bp->b_data, todo, 186 (flags & B_READ) ? 187 VM_PROT_READ | VM_PROT_WRITE : VM_PROT_READ) 188 != KERN_SUCCESS)) { 189 bp->b_flags |= B_ERROR; 190 bp->b_error = EFAULT; 191 goto after_vsunlock; 192 } 193 vmapbuf(bp, todo); 194 195 /* [call strategy to start the transfer] */ 196 (*strategy)(bp); 197 198 /* 199 * Note that the raise/wait/lower/get error 200 * steps below would be done by biowait(), but 201 * we want to unlock the address space before 202 * we lower the priority. 203 * 204 * [raise the priority level to splbio] 205 */ 206 s = splbio(); 207 208 /* [wait for the transfer to complete] */ 209 while ((bp->b_flags & B_DONE) == 0) 210 tsleep((caddr_t) bp, PRIBIO + 1, "physio", 0); 211 212 /* Mark it busy again, so nobody else will use it. */ 213 bp->b_flags |= B_BUSY; 214 215 /* [lower the priority level] */ 216 splx(s); 217 218 /* 219 * [unlock the part of the address space previously 220 * locked] 221 */ 222 vunmapbuf(bp, todo); 223 uvm_vsunlock(p, bp->b_data, todo); 224 after_vsunlock: 225 PRELE(p); 226 227 /* remember error value (save a splbio/splx pair) */ 228 if (bp->b_flags & B_ERROR) 229 error = (bp->b_error ? bp->b_error : EIO); 230 231 /* 232 * [deduct the transfer size from the total number 233 * of data to transfer] 234 */ 235 done = bp->b_bcount - bp->b_resid; 236 #ifdef DIAGNOSTIC 237 if (__predict_false(done < 0)) 238 panic("done < 0; strategy broken"); 239 if (__predict_false(done > todo)) 240 panic("done > todo; strategy broken"); 241 #endif 242 iovp->iov_len -= done; 243 iovp->iov_base = (caddr_t)iovp->iov_base + done; 244 uio->uio_offset += done; 245 uio->uio_resid -= done; 246 247 /* 248 * Now, check for an error. 249 * Also, handle weird end-of-disk semantics. 250 */ 251 if (error || done < todo) 252 goto done; 253 } 254 } 255 256 done: 257 /* 258 * [clean up the state of the buffer] 259 * Remember if somebody wants it, so we can wake them up below. 260 * Also, if we had to steal it, give it back. 261 */ 262 s = splbio(); 263 bp->b_flags &= ~(B_BUSY | B_PHYS | B_RAW); 264 if (nobuf) 265 putphysbuf(bp); 266 else { 267 /* 268 * [if another process is waiting for the raw I/O buffer, 269 * wake up processes waiting to do physical I/O; 270 */ 271 if (bp->b_flags & B_WANTED) { 272 bp->b_flags &= ~B_WANTED; 273 wakeup(bp); 274 } 275 } 276 splx(s); 277 278 return (error); 279 } 280 281 /* 282 * allocate a buffer structure for use in physical I/O. 283 */ 284 struct buf * 285 getphysbuf() 286 { 287 struct buf *bp; 288 int s; 289 290 s = splbio(); 291 bp = pool_get(&bufpool, PR_WAITOK); 292 splx(s); 293 memset(bp, 0, sizeof(*bp)); 294 295 /* XXXCDC: are the following two lines necessary? */ 296 bp->b_rcred = bp->b_wcred = NOCRED; 297 bp->b_vnbufs.le_next = NOLIST; 298 299 return(bp); 300 } 301 302 /* 303 * get rid of a swap buffer structure which has been used in physical I/O. 304 */ 305 void 306 putphysbuf(bp) 307 struct buf *bp; 308 { 309 int s; 310 311 /* XXXCDC: is this necesary? */ 312 if (bp->b_vp) 313 brelvp(bp); 314 315 if (__predict_false(bp->b_flags & B_WANTED)) 316 panic("putphysbuf: private buf B_WANTED"); 317 s = splbio(); 318 pool_put(&bufpool, bp); 319 splx(s); 320 } 321 322 /* 323 * Leffler, et al., says on p. 231: 324 * "The minphys() routine is called by physio() to adjust the 325 * size of each I/O transfer before the latter is passed to 326 * the strategy routine..." 327 * 328 * so, just adjust the buffer's count accounting to MAXPHYS here, 329 * and return the new count; 330 */ 331 void 332 minphys(bp) 333 struct buf *bp; 334 { 335 336 if (bp->b_bcount > MAXPHYS) 337 bp->b_bcount = MAXPHYS; 338 } 339